import sys
from time import sleep
import pygame

from bullet import Bullet
from alien import Alien


def check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets, stats, sb):
    """检查子弹是否击中外星人,击中则删除两者"""
    # 删除碰撞的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, False, True)
    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)
            sb.prep_score()
        check_high_score(stats, sb)
    # 外星人消灭完，重新产生
    if len(aliens) == 0:
        bullets.empty()
        # 消灭完外星人后，加快游戏速度
        ai_settings.increase_speed()
        create_fleet(ai_settings, screen, ship, aliens)
        # 提高等级
        stats.level += 1
        sb.prep_level()


def check_events(sb, ai_settings, screen, stats, play_button, ship, aliens, bullets):
    """响应按键和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, ai_settings, screen, ship, bullets)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(sb, ai_settings, screen, stats, play_button, ship, aliens, bullets, mouse_x, mouse_y)


def check_play_button(sb, ai_settings, screen, stats, play_button, ship, aliens, bullets, mouse_x, mouse_y):
    """玩家点击play按钮开始游戏"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:
        # 重置游戏设置
        ai_settings.initialize_dynamic_settings()
        stats.game_active = True
        # 隐藏光标
        pygame.mouse.set_visible(False)
        # 重置游戏信息
        stats.reset_stats()
        # 清空外星人和子弹
        aliens.empty()
        bullets.empty()
        # 创建新的外星人和飞船
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()
        # 重置记分牌信息
        sb.prep_level()
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_ships()


def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """响应按键"""
    if event.key == pygame.K_q:
        sys.exit()
    # 右移动
    elif event.key == pygame.K_RIGHT or event.key == pygame.K_d:
        ship.move_right = True
    # 左移动
    elif event.key == pygame.K_LEFT or event.key == pygame.K_a:
        ship.move_left = True
    # 空格发射子弹
    elif event.key == pygame.K_SPACE:
        # 创建一颗子弹，加入bullets
        fire_bullet(ai_settings, screen, ship, bullets)


def check_keyup_events(event, ship):
    """响应松开"""
    if event.key == pygame.K_RIGHT or event.key == pygame.K_d:
        ship.move_right = False
    elif event.key == pygame.K_LEFT or event.key == pygame.K_a:
        ship.move_left = False


def update_bullets(ai_settings, screen, ship, aliens, bullets, stats, sb):
    """更新子弹位置，并删除已消失的子弹"""
    # 更新子弹位置
    bullets.update()
    # 删除已消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)
    # 检查子弹是否击中外星人,击中则删除两者
    check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets, stats, sb)


def update_screen(sb, ai_settings, stats, screen, ship, aliens, bullets, play_button):
    """更新屏幕图像，并切换到新屏幕"""
    # 更改屏幕背景色
    screen.fill(ai_settings.bg_color)
    # 在飞船后重绘所有子弹
    for bullet in bullets.sprites():
        bullet.draw_bullet()
    # 绘飞船
    ship.blitme()
    # 绘外星人
    aliens.draw(screen)
    # 显示得分
    sb.show_score()
    # 若游戏处于非活动状态，绘制play按钮
    if not stats.game_active:
        play_button.draw_button()
    # 重新绘制
    pygame.display.flip()


def fire_bullet(ai_settings, screen, ship, bullets):
    """发射子弹"""
    # 创建一颗子弹，加入bullets
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)


def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少外星人"""
    available_spacex_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_spacex_x / (2 * alien_width))
    return number_aliens_x


def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height - (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height))
    return number_rows


def create_alien(ai_settings, screen, aliens, alien_number, row_number):
    """创建一个外星人并放在当前行"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)


def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)
    # 创建第一行外星人
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, row_number)


def change_fleet_direction(ai_settings, aliens):
    """外星人下移，并改变移动方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1


def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘采取相应措施"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break


def update_aliens(sb, ai_settings, stats, screen, ship, aliens, bullets):
    """更新外星人位置"""
    check_fleet_edges(ai_settings, aliens)
    aliens.update()
    # 检测外星人与飞船碰撞
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(sb, ai_settings, stats, screen, ship, aliens, bullets)
    # 检测外星人到达屏幕低端
    check_aliens_bottom(sb, ai_settings, stats, screen, ship, aliens, bullets)


def ship_hit(sb, ai_settings, stats, screen, ship, aliens, bullets):
    """响应外星人撞到飞船"""
    if stats.ships_left > 1:
        # ship_left 减 1
        stats.ships_left -= 1
        sb.prep_ships()
        # 清空外星人和子弹
        aliens.empty()
        bullets.empty()
        # 创建新的外星人和飞船
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()
        # 暂停
        sleep(.5)
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)


def check_aliens_bottom(sb, ai_settings, stats, screen, ship, aliens, bullets):
    """检查外星人到达屏幕底部"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            # 像飞船被撞到一样进行处理
            ship_hit(sb, ai_settings, stats, screen, ship, aliens, bullets)
            break


def check_high_score(stats, sb):
    """检测是否超过最高分"""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score()
